cppLogic errorMedium

std::sort comparator violates strict weak ordering

Time: 0:00

BugFind the bug and fix the code

What it should do

Sort integer vector in descending order. Example: sortVectorDescending([2, 5, 1]) -> [5, 2, 1]

What happens instead

Segmentation fault or heap corruption in std::sort with <= operator

#include <iostream>
#include <vector>
#include <algorithm>

std::vector<int> sortVectorDescending(std::vector<int> nums) {
    // <= violates strict weak ordering (comp(x, x) must be false)
    std::sort(nums.begin(), nums.end(), [](int a, int b) {
        return a >= b;
    });
    return nums;
}

int main() {
    std::vector<int> res = sortVectorDescending({2, 5, 1});
    return 0;
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

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Hint 3

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This bug belongs to the logic errors pattern

The wrong operator, an inverted condition, a formula the right way round but backwards.

Learn the logic errors pattern Step through your own code

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#include <iostream> #include <vector> #include <algorithm> std::vector<int> sortVectorDescending(std::vector<int> nums) { // <= violates strict weak ordering (comp(x, x) must be false) std::sort(nums.begin(), nums.end(), [](int a, int b) { return a >= b; }); return nums; } int main() { std::vector<int> res = sortVectorDescending({2, 5, 1}); return 0; }

std::sort comparator violates strict weak ordering

What it should do

What happens instead

More logic errors to practise

std::sort comparator violates strict weak ordering

What it should do

What happens instead

More logic errors to practise